1. Field of the Invention
The present invention relates to a fundus observation device for observing the state of the fundus oculi of an eye, and a program controlling the same.
2. Description of the Related Art
As a fundus observation device, conventionally, a fundus camera has been widely used. FIG. 11 shows one example of the appearance of a conventional generally-used fundus camera, and FIG. 12 shows one example of an optical system composition to be internally accommodated in the fundus camera (e.g. JP Patent laid-open No. 2004-350849). Herein, “observation” includes at least a case in which produced fundus images are observed (fundus observations with the naked eye may be included).
First, referring to FIG. 11, an explanation will be made regarding the appearance of a conventional fundus camera 1000. This fundus camera 1000 is provided with a platform 3 mounted on a base 2 so as to be slidable in the front and rear, right and left directions (horizontal direction). On this platform 3, an operation panel 3a and a control lever 4 are installed for an examiner to conduct various operations.
The examiner can 3-dimensionally move the platform 3 on the base 2 by operating the control lever 4. On the top of the control lever 4, an operation button 4a is installed to be pressed down to obtain fundus oculi images.
On the base 2, a post 5 is installed standing upwards. On the post 5, a jaw rest 6 where the jaw of a patient is to be rested and an external fixation lamp 7 emitting light for fixing an eye E are provided.
On the platform 3, a main body part 8 is installed to accommodate various optical systems and control systems of the fundus camera 1000. The control system may be installed inside the base 2 or the platform 3, etc., or in an external device such as a computer connected to the fundus camera 1000.
On the side of the eye E of the main body part 8 (the left side of the page in FIG. 11), an objective lens part 8a disposed opposite to the eye E is installed. Also, on the examiner's side of the main body part 8 (the right side of the page in FIG. 11), an eyepiece part 8b for observing the fundus oculi of the eye E with the naked is installed.
Furthermore, the main body part 8 is provided with a still camera 9 for producing a still image of a fundus oculi of the eye E and an imaging device 10 such as a TV camera for producing still images or moving images of a fundus oculi. The still camera 9 and the imaging device 10 are formed so as to be removable from the main body part 8.
As the still camera 9, in accordance with various conditions such as the purpose of an examination or the saving method of produced images, a digital camera equipped with imaging elements such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), a film camera, and an instant camera, etc. may interchangeably be used when it is appropriate. The main body part 8 is equipped with a mounting part 8c for interchangeably mounting various kinds of still camera 9.
If the still camera 9 or the imaging device 10 is for taking digital images, the image data of the produced fundus image can be sent to a device such as a computer connected to the fundus camera 1000 and be observed as a fundus image displayed on the display. Also, the image data can be sent to an image storing device connected to the fundus camera 1000 to compile a database and be used as electronic data for creating medical charts, etc.
Furthermore, on the examiner's side of the main body part 8, a touch panel monitor 11 is installed. On this touch panel monitor 11, fundus images of the eye E created based on the video signals output from the (digital-type) still camera 9 or imaging device 10 are displayed. Moreover, on the touch panel monitor 11, a 2-dimensional coordinate system with the center of the screen as the origin is displayed overlapped with a fundus image. When the examiner touches a desired position on the screen, the coordinate value corresponding to the touched position is displayed.
Next, referring to FIG. 12, a composition of an optical system of the fundus camera 1000 will be described. The optical system of the fundus camera 1000 is aligned with the fundus oculi Ef (that is, the optical system is moved in the x-direction, the y-direction, and the z-direction shown in FIG. 12 to be placed at a position appropriate for imaging) before imaging the fundus oculi Ef of the eye E. The optical system of the fundus camera 1000 is provided with an illumination optical system 100 to light the fundus oculi Ef of an eye E, an imaging optical system 120 to guide the fundus reflection light of the illumination light to the eyepiece part 8b, the still camera 9 and the imaging device 10.
The illumination optical system 100 comprises: an observation light source 101; a condenser lens 102; an imaging light source 103; a condenser lens 104; exciter filters 105 and 106; a ring transparent plate 107; a mirror 108; a liquid crystal display (LCD) 109; an illumination diaphragm 110; a relay lens 111; an aperture mirror 112; and an objective lens 113.
The observation light source 101 is composed of a halogen lamp, etc. and emits ambient light (continuous light) for observing the fundus oculi. The condenser lens 102 is an optical element for converging the ambient light (observation illumination light) emitted by the observation light source 101 and substantially evenly irradiating the observation illumination light to the fundus oculi.
The imaging light source 103 is composed of a xenon lamp, etc. to be flashed at the time of production of fundus oculi Ef images. The condenser lens 104 is an optical element for converging the flash light (imaging illumination light) emitted by the imaging light source 103 and irradiating the fundus oculi Ef evenly with the imaging illumination light.
The exciter filters 105 and 106 are filters used at the time of fluorography of images of a fundus oculi Ef. The exciter filters 105 and 106 can respectively be inserted into and removed from an optical path by a drive mechanism (not shown) such as a solenoid. The exciter filter 105 is placed on the optical path in the event of FAG (fluorescein angiography). Whereas, the exciter filter 106 is placed on the optical path in the event of ICG (indocyanine green angiography). Furthermore, when color images are to be obtained, both exciter filters 105 and 106 are retracted from the optical path.
The ring transparent plate 107 is placed in a conjugating location with a pupil of the eye E, and is equipped with a ring transparent part 107a taking an optical axis of the illumination optical system 100 as a center. The mirror 108 reflects the illumination light emitted by the observation light source 101 or by the imaging light source 103, in the direction of the optical axis of the imaging optical system 120. The LCD 109 displays a fixation target (not illustrated) for fixing the eye E.
The illumination diaphragm 110 is a diaphragm member to shut out part of the illumination light in order to prevent flare, etc. This illumination diaphragm 110 is composed so as to be movable in the light axial direction of the illumination optical system 100, and is thus capable of changing an illumination region of the fundus oculi Ef.
The aperture mirror 112 is an optical element to combine an optical axis of the illumination optical system 100 and an optical axis of the imaging optical system 120. In the center region of the aperture mirror 112, an aperture 112a is opened. The optical axis of the illumination optical system 100 and the optical axis of the imaging optical system 120 cross each other at a substantially central location of this aperture 112a. The objective lens 113 is installed in the objective lens part 8a of the main body part 8.
The illumination optical system 100 having such a composition illuminates the fundus oculi Ef in the following manner. First, at the time of fundus observation, the observation light source 101 is turned on and the observation illumination light is emitted. This observation illumination light is applied to the ring transparent plate 107 through the condenser lenses 102 and 104. (The exciter filters 105 and 106 are removed from the optical path.) The light passed through the ring transparent part 107a of the ring transparent plate 107 is reflected by the mirror 108, and after passing through the LCD 109, the illumination diaphragm 110 and the relay lens 111, reflected by the aperture mirror 112. The observing illumination light reflected by the aperture mirror 112 advances in the optical axial direction of the imaging optical system 120, and is converged by the objective lens 113 to enter the eye E, thereby illuminating the fundus oculi Ef.
At this moment, the ring transparent plate 107 is placed in a conjugating location with the pupil of the eye E and, on the pupil, a ring-shaped image of the observation illumination light entering the eye E is formed. The fundus reflection light of the observation illumination light is to be emitted from the eye E through a central dark part of the ring-shaped image on the pupil. Thus, an effect of observing illumination light entering the eye E on the fundus reflection light of the observing illumination light is prevented.
On the other hand, at the time of imaging of the fundus oculi Ef, flush light is emitted from the imaging light source 103 and the imaging illumination light is applied to the fundus oculi Ef through the same path. In the event of photofluographing, either the exciter filter 105 or the exciter filter 106 is placed selectively on the optical path, depending on whether FAG imaging or ICG imaging is carried out.
Next, the imaging optical system 120 will be described. The imaging optical system 120 comprises: an objective lens 113; an aperture mirror 112 (an aperture 112a thereof); an imaging diaphragm 121; barrier filters 122 and 123; a variable magnifying lens 124; a relay lens 125; an imaging lens 126; a quick return mirror 127; and an imaging media 9a. Herein, the imaging media 9a is any imaging media (an image pick-up element such as CCD, a camera film, an instant film, etc.) used for the still camera 9.
The fundus reflection light of the illumination light, exiting from the eye E through the central dark part of the ring-shaped image formed on the pupil, enters the imaging diaphragm 121 through the aperture 112a of the aperture mirror 112. The aperture mirror 112 reflects cornea reflection light of the illumination light, and acts so as not to mix the cornea reflection light into the fundus reflection light entering the imaging diaphragm 121. As a result, generation of flare on the observation images and/or produced images is prevented.
The imaging diaphragm 121 is a plate-shaped member having a plurality of circular light transparent parts of different sizes. The plurality of light transparent parts compose diaphragms with different diaphragm values (F value), and are placed alternatively on the optical path by a drive mechanism (not illustrated herein).
The barrier filters 122 and 123 can be inserted into and removed from the optical path by a drive mechanism (not illustrated) such as a solenoid. In the event of FAG imaging, the barrier filter 122 is placed on the optical path, whereas in the event of ICG imaging, the barrier filter 123 is placed on the optical path. Furthermore, at the time of production of color images, both the barrier filters 122 and 123 are retracted from the optical path.
The variable magnifying lens 124 is movable in the light axial direction of the imaging optical system 120 by a drive mechanism (not illustrated herein). This makes it possible to change the magnifying ratio of an observation and the magnifying ratio in imaging, and to focus images of a fundus oculi. The imaging lens 126 is a lens to focus the fundus reflection light from the eye E onto the imaging media 9a. 
The quick return mirror 127 is disposed rotatably around a rotary shaft 127a by a drive mechanism not illustrated herein. In the event of imaging a fundus oculi Ef with the still camera 9, the fundus reflection light is guided to the imaging media 9a by springing up the quick return mirror 127 obliquely mounted on the optical path. Whereas, in the event of imaging a fundus oculi with the imaging device 10 or of observing the fundus oculi with the naked eye of the examiner, the quick return mirror 127 is obliquely mounted on the optical path to upwardly reflect the fundus reflection light.
The imaging optical system 120 is further provided, for guiding the fundus reflection light reflected by the quick return mirror 127, with a field lens 128, a switching mirror 129, an eyepiece 130, a relay lens 131, a reflection mirror 132, an imaging lens 133, and an image pick-up element 10a. The image pick-up element 10a is an image pick-up element such as CCD installed internally in the imaging device 10. On the touch panel monitor 11 a fundus oculi image Ef′ imaged by the image pick-up element 10a is displayed.
The switching mirror 129 is rotatable around a rotary shaft 129a, as well as the quick return mirror 127. This switching mirror 129 is obliquely disposed on the optical path during observation with the naked eye, and reflects the fundus reflection light to the eyepiece 130.
Also, when a fundus image is formed by using the imaging device 10, the switching mirror 129 is retracted from the optical path, and the fundus reflection light is guided toward the image pick-up element 10a. In this case, the fundus reflection light is directed toward the relay lens 131, reflected by the mirror 132, and focused onto the image pick-up element 10a by the imaging lens 133.
The fundus camera 1000 is a fundus observation device used for observing the state of the surface of a fundus oculi Ef, that is, the retina. In other words, the fundus camera 1000 is a device to obtain a 2-dimensional fundus oculi image when it sees the fundus oculi Ef from a direction of the corneal on the eye E. On the other hand, in the deep layer of retina tissues such as the choroidea or sclera exist, and a technology for observing these deep layer tissues has been desired. In recent years, devices for observing these deep layer tissues have been practically implemented (e.g. JP Patent laid-open No. 2003-00543, JP Patent laid-open No. 2005-241464).
The fundus observation devices disclosed in JP Patent laid-open No. 2003-00543 and JP Patent laid-open No. 2005-241464 are devices (referred to as an optical image measurement device, an optical coherence tomography device, and the like) to which so-called OCT (Optical Coherence Tomography) technology is applied. Such a fundus observation device is a device splitting low coherence light into two, guiding one of the lights (signal light) to a fundus oculi and the other (reference light) to a given reference object, and detecting and analyzing interference light obtained by overlaying the signal light through the fundus oculi and the reference light through the reference object, thereby forming tomographic images of the surface and deep layer tissue of the fundus oculi. Further, the optical measuring device is capable of forming a 3-dimensional image of the fundus oculi based on a plurality of tomographic images. These devices are generally called a Fourier domain OCT.
The Fourier domain OCT is designed to scan the signal light to irradiate the fundus oculi, thereby form a tomographic image having a depth-wise (z-direction shown in FIG. 12) cross section along a scanning line. Such scanning of the signal light is referred to as a B-scan (see NEDO Workshop “Seeing (examining) inside the body from the ‘window’ of the human body, the fundus oculi”—Development of an ultra early diagnostic device for lifestyle-related diseases using the latest optical technologies (held on Apr. 25, 2005), Internet, URL: http://www.nedo.go.jp/informations/koubo/170627—2/besshi3.pdf>).
When forming a 3-dimensional image, the Fourier domain OCT performs the B-scan along a plurality of scanning lines, and applies an interpolation process to the plurality of tomographic images obtained by the B-scan, thereby generating 3-dimensional image data. This 3-dimensional image data is referred to as volume data, voxel data or the like, as well as in a medical imaging diagnosis device such as an X-ray CT device. The 3-dimensional image data is image data in a form in which pixel data (e.g. luminance value and RGB value regarding brightness, contrasting density and color) is assigned to each of voxels arranged 3-dimensionally. A 3-dimensional image is displayed as a pseudo 3-dimensional image seen from a certain viewing angle obtained by rendering volume data.
Not only in opthalmology but generally in the medical field, an identical site of a patient is observed multiple times (hereinafter, may be referred to as “course observation or the like”), for example, in therapeutic course observation or preoperative and postoperative observation.
In the course observation or the like of the fundus oculi, in order to observe a noted site on the fundus oculi, such as the macular area, optic papilla and a detached site of retina, multiple times, it is necessary to specify the position of the noted site and capture an image at each observation time.
Regarding a site that is a landmark on the fundus oculi, such as optic papilla, it is easy to specify the position thereof. However, there exists a noted site whose position is difficult to specify simply by observing the image. Particularly, when the noted site exists in a deep layer (such as choroid membrane and sclera) of the fundus oculi, it is more difficult to specify the position of the noted site than when the noted site exists on the surface of the fundus oculi.
In addition, in the course observation or the like, it is preferable to photograph images at each time under the same conditions. For example, in an optical image measuring device, it is desired that various conditions such as the fixation position of an eye and a scan of signal lights (scanning position or scanning pattern) are the same.
However, it is very troublesome to specify the position of a noted site for each photograph and to manually input various conditions. In addition, an inadvertent mistake may intervene, such as forgetting to record the position of a noted site and photographing conditions, or making a mistake in setting the position or conditions.